Field of the Invention
The present invention refers to a method for removing material from metal workpieces moved relative to the removal tool, in particular for cutting sheet metal, comprising the step of preheating, without melting, the surface of the workpiece to a temperature at which ignition is triggered by a combustible gas which is blown onto the preheated section as a jet under pressure and by means of which burnt material of the workpiece is blown away from a cut recess produced by such burning.
Such a method is used in autogenous gas cutting processes. The preheating of the surface of the workpiece to the ignition temperature of said workpiece is carried out by means of a heating gas, e.g. a gas mixture consisting of acetylene and oxygen. The melting point is not reached during this preheating process. It is regarded as being essential that energy of the heating gas also penetrates into the kerf. The combustible gas used is oxygen by means of which the material of the workpiece is burnt to oxide. The oxide is blown away by the pressure of the combustible gas. A kerf or a cut recess having smooth walls is produced.
In the generally known laser beam gas cutting process, a jet of combustible gas and a laser beam which is coaxial with said gas jet are used for cutting sheet metal. When this laser beam gas cutting process is used for sheet metal thicknesses of less than 20 mm, the cutting speed can be increased in comparison with conventional autogenous gas cutting processes. The quality of cut faces of thicker plates, however, will be less good. When plates having a thickness of approx. 10 mm and higher are cut, the number of burnt-out cavities will increase and the averaged peak-to-valley heights will frequently exceed 100 .mu.m. Burnt-out cavities and surface roughnesses originate from turbulences caused on the removal front due to the incident laser radiation during melting and burning. The turbulences occurring will also reduce the cutting speed.